Howell first became MP for Henley at the
2008 by-election, when the newly elected Mayor of London
Boris Johnson resigned as MP. Following his retaining his seat at the 2010 general election, Howell was appointed the
Parliamentary Private Secretary to the
Leader of the House of Commons and the
Lord Privy Seal, then Sir
George Young, Bt. He served on the Work and Pensions Select Committee and Justice Committee. In 2012 Howell reported receiving death threats after responding to a question on whether he would be acting to try to halt Israeli military actions with a reference to Hamas rocket attacks in an online exchange. Howell was a member of the Parliamentary Group of the Conservative Friends of Israel. Howell declared having received free flights to and accommodation in Israel in 2012, 2015, 2016, 2018 and 2019. Howell was opposed to Brexit prior to the
2016 referendum. He voted in favour of the withdrawal agreement of the UK from the EU, and advocated against a second referendum to ensure the referendum result was honoured. At the Conservative Party Conference in 2017, he was quoted by the
Henley Standard as saying: "My message to Boris is to keep his bloody mouth shut!" regarding Johnson's demand that the post-Brexit transition should last "not a second longer" than two years. A year later, at the party conference in 2018, when
Theresa May was reportedly being undermined by Johnson,
The Guardian reported Howell as saying: "As far as I'm concerned Boris can just fuck off." In 2019, following the election of Johnson to the leadership of the Conservative Party, Howell was quoted by the
Henley Standard as saying: "Boris has been elected by a large majority of the party members and I'm a democrat and we must follow that." In the
July–September 2022 Conservative Party leadership election, Howell backed
Rishi Sunak to replace
Boris Johnson. Howell said he supported
Liz Truss after her victory. In 2023, Howell criticised the proposed construction of a large solar farm in Botley West. Howell confirmed on 11 April 2023 that he would not stand for re-election at the
2024 general election, citing old age and his intention to pursue "other avenues". ==Other interests==